Time Machine failing due to /private/var/db/CoreDuet/Knowledge/KnowledgeC.db

M1 14" Macbook Pro

My Time Machine is failing to back up because of the above file. I found a workaround with some terminal commands to exclude the file, but TERMINAL is saying it needs full disk access to execute the command. It definitley has FDA in settings (alwasy has), and I have switched it on and off, re-booted, booted in safe mode, and still, it says it doesn't...

I am at the end of my knowledge and wondered if anyone has any experience of this?

I really just want TM to back up, but I have ended up trying to get Terminal commands to work and going down that rabbit hole!

Many thanks for any help,